Sunday, January 27, 2008

Mostly a travelog here. Yesterday, Saturday, was our one-day excursion to the Pyramids of Giza. It was wonderful, impressive and inspiring. After a long bus ride from Alexandria to Giza, we visited the site of the great pyramids and sphinx. We were permitted to enter the great pyramid of Kheops and climb to the large hall in the inside. Let me just say that even though I have seen many television documentaries about the pyramids, so I know what it is like visually, there is still something humbling to be standing in the same hallway built thousands of years ago. The Egyptian students feel a strong respect for their ancestors, which I appreciated.

Afterwards, we entered the museum of the solar boat, sitting next to the great pyramid. The timbers of the boat look maybe 200 years old, not many thousands!

The area is a strange chaotic mix of the encroaching city, which basically comes right to the doorstep of the pyramids; the rustic majesty of the pyramids themselves; and the unfortunate flocks of souvenir hucksters.

At that point, we realized we had lost one of our group, who we eventually abandoned. Eventually we found out that he left the pyramid site and took the train back to Alexandria by himself!

After that, we had a conference dinner with University of Cairo officials, and also members of the Egyptian science ministry. It was a long day, but I'm glad I went.

Friday, January 25, 2008

There is nothing more strange than to visit your friend Google in a foreign country, and find that all the words are squiggly backwards!

Since I am staying in Egypt, Google automatically converts to Arabic mode, which has writing from right-to-left. It's a new experience to be typing on the right hand side of the search box instead of the left.

I arrived in Egypt on Sunday, and it's already Friday! I'm participating in a workshop to train young African and Middle Eastern students in the techniques of X-ray and gamma-ray astronomy. The workshop is being held at the New Library of Alexandria, which of course has the library and also a planetarium and museum. Alexandria is located at the Mediterranean coast, and the library is right at the coast. The library is shown by night (with moonlight glinting from the reflecting pool.

So far I haven't actually done much sight-seeing since we are focussed on helping the students. I have learned one small strip of Alexandria between the hotel and the Library very well, and nothing else!

The conference hotel describes itself as a "heritage hotel" in its brochure. As far as I can tell, this is a kind way of saying that it has lofty goals of being a high-class establishment, but is slowly falling apart. In my room, both a telephone and lamp are non-working.

We will be visiting the pyramids of Giza tomorrow for a day-long excursion. Hopefully I will find some nice souvenirs. However, I think the nicest souvenir would be to get a library card for the Library of Alexandria.

The one time I visited Philadelphia, I got an parking ticket for being about three minutes over time limit. It was especially frustrating because I had just arrived in the city, parked in a 10-minute loading zone, went straight up to my friend's apartment to fetch her, and came straight back down to move my car. Now I see why I got the ticket.

The new reality television show Parking Wars reveals that Philadelphia parking enforcers are literally hiding and waiting for parking limits to expire. (Unfortunately the producers didn't go with my Scab Pickers reality show concept, and did parking instead.)

I was ticked off enough that I made out my check to the "Money Grubbing City of Philadelphia." And they cashed it. Good thing I didn't cross the line between annoying and obscene.

Sunday, January 13, 2008

OK, so I finally gave up on my old Camry. It has served me well through almost eight years, but it was time to move on. Thank you Camry!

The new car is a friendly little used hybrid Prius that I bought from a person in Virginia. Vis:So far I am quite happy with it. The previous owner took very good care of the car. When a friend got in the car he exclaimed, "Dude! Are you sure this is not new?"

It's a very geeky car. It's all about saving energy. When the car comes to a rest at a stoplight, the engine turns completely off, which is a bit disconcerting. When starting up again, the electric motor and battery can get you going, but the internal combustion engine starts (silently!) if you want to accelerate quickly or go over about 30 MPH. The "brakes" are actually regenerative brakes that use the electric motor as a generator to save your kinetic energy in the battery.

My favorite geeky part is the Star Trek-type visual displays in the on-board computer:How do I re-route the ODN conduit?

Saturday, January 12, 2008

Follow along as I explore trying to make my house a little more energy efficient, look at my energy usage history, and do a little thermodynamics. There will be some small equations, but I'll explain them in words as well. At the end, I discover something about the insulation efficiency of my house.

I live in a region which is heating-challenged. Every house or apartment I've lived in has had issues with heating in the winter and cooling in the summer. Builders in this area just don't seem to get that a little insulation goes a long way. For my current house, the homeowner's association also decided in its infinite wisdom that it would rip out all the old oil-fired boilers because they were too expensive, and replace them with electric baseboard heaters, because they are more economical. Whatever insane reasoning that led to that decision is now negated, especially since electricity has doubled in price over the past two years here. While it is true that electric heaters themselves are 100% efficient, the power plant and transmission lines are not. Furthermore, baseboard heaters tend to be mounted on outer walls below windows, so much of the heat can be conducted through the wall and escape the house.

I'm trying a few new strategies to try to make my house more comfortable, given its current limitations. First, I added transparent window films to almost all of the windows. The idea is that they hold an still pocket of air against the window, which adds an extra insulation factor. They also can contain small drafts so that cold air can't get in. It does take some work to install them, which basically involves stretching a huge sheet of saran wrap onto double stick tape mounted on each window frame, but eventually I developed a pretty efficient method (especially for smoothing the wrinkles).

A second thing I did was install curtains in the living room doorways, in order to keep the heat from escaping to colder parts of the house from the room I use most. These are cheap but heavy curtains I got on sale at Wal-Mart, hung from an expandable shower curtain rod across two doorways. Finally, I put some foam-board over my back door. It's a thin wooden door that conducts a lot of heat out.

I think these efforts have helped in a very qualitative sense. The living room is much less drafty, especially near the windows. Before installing the films, a cold down-draft from the windows would collide from an up-draft from the heaters to make chilly turbulent zone right where I was sitting. These drafts are gone now. The curtains also definitely help keep the heat where I appreciate it most.

Comfort is good, but I'd also like to know if this is saving energy and money.

PEPCO kindly puts my energy usage history on each bill, so it was a matter of collecting a few old bills and entering them in the computer. That's shown in black below (click for larger image).

The plot shows the number of kiloWatt-hours I use each month (ignore the red and blue curves for the moment). Unfortunately, I don't have data yet for December, the first month that I installed the window films or curtains, so I have to put the efficiency question on hold for now.

I decided to check out this plot a little more carefully. I use the greatest energy in the winter, obviously for heating. There are also small bumps in the summer, corresponding to cooling. Up until recently, I had a very old air conditioner which I rarely used, so my cooling expenses have never been large.

What to compare this with? Well, the there is a nifty number called a heating degree day used for heating calculations. Basically, any day that the mean temperature dips below 65 degrees Fahrenheit is considered a "heating day," and for that matter when the mean temperature is above 65 it is a "cooling day." The number of heating degree days is the number of degrees the mean temperature is below 65. The US National Climatic Data Center (not to be confused with the Climactic Data Center! Ooo la lah!) provides tabulated historical heating and cooling degree day data. The monthly total heating and cooling degree days are shown in the above plot (red=heating; blue=cooling; averaged over Maryland & Washington DC).

It's no big surprise that the heating and cooling curves match up with my energy usage pretty well. It's physics after all.

In fact, the Mr. Quantitative in me wants to do more. I decided to perform a linear regression between these quantities, with energy usage per day as the dependent variable, and heating/cooling degree days per day as the two independent variables. The simple function I tried was:

E = Constant + H(Th) + C(Tc)

where H(Th) is some function of heating degree days (per day), and C(Tc) is another function of cooling degree days (per day), both of which describe power usage versus temperature. This equation has the interpretation that I use some constant electric power all the time (for lights, water heater, etc.), plus the amount I use for heating and cooling, which depend on temperature.

The obvious choice is to make the two electric heating functions, H and C, proportional to temperature. However, I found that wasn't a good fit, as you will see below. Instead, there is an activation threshold. For small temperature excursions, no heating or cooling is required, and I don't use energy. This would be my comfort zone, the temperature range I'm willing to tolerate. I imagine I have a larger comfort zone than many people. As the outside temperature gets more extreme, then I use energy to maintain the inside house temperature within the comfort range. This function can be written as a constant when the heating/cooling temperature is within the comfort threshold, and a linear function outside of that. The linear coefficient of the function describes the number of kiloWatt-hours per day needed to heat (or cool) the house one extra degree Fahrenheit.

The fit works quite well, and here is how the results look. On the heating side, the function H(T) looks like this:This means that I am willing to tolerate mean outside temperature drops of about 6.5 degrees (F) below the baseline temperature of 65 degrees before turning on the heat, and then I use about 0.84 kWh of energy per day for each degree (F) that it gets colder. At the current PEPCO price of 10.96 cents/per kWh, I pay an extra 10 cents per day for each degree colder that the outside temperature goes below about 59 degrees.

On the cooling side, the curve looks like this:I'm apparently willing to tolerate large excursions before turning on the air conditioner (up to 10 degrees above the 65 degree baseline), and then I use 1.31 kWh of energy per day for each degree above that (for a cost of about 14 cents per day for each degree).

Finally, it's worth noting that I use 9.7 kWh of energy every day, no matter what the outside temperature is, just keeping the house going. I know for a fact that my refrigerator uses about 3.8 kWh every day on average, or about 40% of the total. It's a very old refrigerator from 1982 (!) which needs to be replaced. I used my handy Kill-a-Watt energy meter to measure this and other devices in the house. The refrigerator is by far the largest constant energy user.

Interestingly, last winter I changed from incandescent and halogen lamps to compact fluorescent bulbs. I predict this should save me between 1-2 kWh per day. A change such as this is barely detectable on the graphs, given the season and monthly fluctuations.

As one final exercise, I can estimate the overall efficiency my house, the effective "R-value". This quantity is defined as the reciprocal of the amount of heat lost per unit time per exposed area per degree temperature change, and has units of ft2 per (BTU/hour/Fahrenheit). I already know the second quantity, since it's the linear heating coefficient I found above (0.845 kWh/day/F = 120 BTU/hour/F). The exposed area of my house is about 2000 ft2, giving an effective R-value of 17. (NOTE 14 Jan: my original value of R-0.7 was had a unit conversion error and was incorrect).

An overall insulation efficiency of R-17 is okay but not great. As pointed out here, a house in my region (zone 2) demands an R value in the range of 18 (walls) to 49 (attic). However, as one of my commenters notes, there are other factors to consider, like how much air circulates through the building.

Remember that this data is all based on my house before I made the few changes above. Neither my usage data nor the climate data for the winter heating season are available yet. I hope to see improved efficiency!

Update (14 Jan): Oops! I made a unit error when converting from kWh/day to BTU/hr (missed a factor of 24). After the correction, the overall insulation efficiency of R-17 is more reasonable.

Sunday, January 6, 2008

Since 1999, I have been the proud owner of a Toyota Camry, which my parents graciously gave it to me. This Camry was born in 1992 and has had a string of owners, starting with as corporate fleet, then to some other wanker, then my parents, and now me. It startles me to think that this car pre-dates the beginning of The X-files!

Well, gradually over the years, this car has been becoming more difficult to maintain. I try to do the standard up-keep, but more and more things are starting to fail.

The most recent failure is the passenger side window motor. Unfortunately for the current season (winter), the window has failed in the most awkward state (open), which can make for uncomfortable driving (breezy). The driver-side window failed a few years ago, so it's likely that the other window motors will go bad at some stage. It also means that I can't keep anything valuable inside the car, and it certainly isn't waterproof when it rains, like it did last night. On the positive side, I don't have to preoccupy myself with locking up!

Surely, as this is a very old car, there are many components that are near their failure threshold. And, as any rider of my car knows, I also just live with some of its (er) shortcomings. It's just a matter of time before more things go bad. The question is, how long do I keep dumping money into it for repairs?

Over the past few years, I've become more conscious of this problem. I've justified it to myself on the basis of, this $X repair will keep me going for another year. Last summer I spent a considerable amount on some repairs, with a certain amount of resolve that it would be the last time. So here I am, less than a year later, and something new has come up.

My friends and colleagues all say, "Dude, just get a new car!" Good point, but I'm way too analytical to just do that.

Unlike my first car, a Nissan Sentra (also a gift from my parents! Thanks again!), I don't have as much of an emotional attachment to the Camry. So from an emotional standpoint, I'm probably willing to let go.

Economically, the amount of repair work required to get the car into a "good" condition is approximately equal to its re-sale value if it were in good condition. So from that perspective, its probably worthless to me.

From a timing standpoint, it's good in a way. I have some travel coming up, where I wouldn't need a car anyway. On the other hand, it would have been "nicer" for this to happen in December. I could have donated the car to charity, taken a tax break for 2007, and bought a car at the end of the calendar year when it might have been easier to get a good deal.

From a personal convenience standpoint, it's not so great. I'm the kind of person that takes forever to buy a can of shaving cream, much less deciding on ditching a car and buying a new one. I don't relish spending my time visiting car dealerships, or going through the hassle of buying a used car.

There is no magic conclusion here, but my gut is telling me it's time to trow in the towel.